矿物质氧化物对燃煤烟气中砷/铅的吸附特性研究

选取典型的矿物质氧化物为吸附剂，在两段式固定床反应器中研究了模拟烟气气氛下吸附剂吸附As₂O₃、PbO的特性，吸附反应的原子态密度、吸附位、吸附能等通过密度泛函理论（DFT）计算获得。结果表明，CaO的砷吸附容量最大，900 ℃吸附砷容量为5.25 mg/g；其次是Fe₂O₃、MgO、Al₂O₃，吸附的砷以As³⁺和As⁵⁺的砷酸盐形式存在，高岭土和飞灰具有较大的PbO吸附容量，最大吸附容量分别为6.69和2.75 mg/g；其次是SiO₂和Al₂O₃，并且50%SiO₂/50%Al₂O₃ 混合吸附剂的铅吸附容量高于单一氧化物，吸附剂表面O原子是As₂O₃的吸附活性位点，吸附剂暴露的不饱和Si和Al原子是PbO的吸附活性位点，此外温度、烟气气氛对吸附容量和吸附产物有显著影响。

Study on arsenic/lead adsorption characteristics by mineral oxides in coal-fired flue gas

The As₂O₃ or PbO adsorption characteristics using typical mineral oxides as the sorbents were studied in a two-stage fixed-bed reactor under a simulated flue gas, and the density of atomic states, adsorption sites, and adsorption energy for the adsorption reaction were calculated by density functional theory (DFT). The results demonstrate that CaO has a large As₂O₃ adsorption capacity, with an arsenic adsorption capacity of 5.25 mg/g at 900 ℃, followed by Fe₂O₃, MgO, and Al₂O₃; and the adsorbed arsenic exists in the form of As³⁺ and As⁵⁺ arsenates. Kaolin and fly ash have large PbO adsorption capacities, with the maximum lead adsorption capacities of 6.69 and 2.75 mg/g, respectively, followed by SiO₂ and Al₂O₃, and the adsorption capacity for lead with the 50%SiO₂/50%Al₂O₃ mixture is higher than that with their single oxide. The oxygen atoms on the surface of the sorbents are the active sites for As₂O₃ and the unsaturated Si and Al atoms exposed on the surface of the sorbents are the active sites for PbO. In addition, the adsorption temperature and flue gas atmosphere have significant effects on the adsorption capacity and adsorption products of the sorbents.